Summary

Multilingualism—the ability to understand and speak several languages—is exceptional in the United States but common elsewhere, especially in small-scale traditional societies. For instance, once while I was camped with some New Guinea Highlanders conversing simultaneously in several local languages, I asked each man to name each language in which he could converse. It turned out that everyone present spoke at least 5 languages, and the champion was a man who spoke 15. What are the cognitive effects of such multilingualism? Recent studies (1–5) show that children raised bilingually develop a specific type of cognitive benefit during infancy, and that bilingualism offers some protection against symptoms of Alzheimer's dementia in old people.